Radioiodine-131 Therapy Used for Differentiated Thyroid Cancer Can Impair Titanium Dental Implants: An In Vitro Analysis.

BACKGROUND: The aim was to assess, in vitro, the effects of radioiodine-131 (I-131) on the structure of titanium implants. MATERIAL AND METHODS: A total of 28 titanium implants were divided into 7 groups (n = 4) and irradiated at 0, 6, 12, 24, 48, 192 and 384 hours. At the end of the experiment, each sample was investigated via scanning electron microscopy (SEM) and electrochemical measures. RESULTS: The control sample revealed a smooth and compact surface. The small micro-sized porosity is slightly visible at the macroscopic level, but the precise details cannot be observed. A mild exposure to the radioactive solution for 6 to 24 h showed a good preservation of the macro-structural aspects such as thread details and surface quality. Significant changes occurred after 48 h of exposure. It was noticed that the open-circuit potential (OCP) value of the non-irradiated implants move toward more noble potentials during the first 40 min of exposure to the artificial saliva and then stabilizes at a constant value of -143 mV. A displacement of the OCP values toward more negative values was observed for all irradiated implants; these potential shifts are decreasing, as the irradiation period of the tested implants increased. CONCLUSION: After exposure to I-131, the structure of titanium implants is well preserved up to 12 h. The eroded particles start to appear in the microstructural details after 24 h of exposure and their numbers progressively increase up to 384 h after exposure.

Combined Electrochemical, Raman Analysis and Machine Learning Assessments of the Inhibitive Properties of an 1,3,4-Oxadiazole-2-Thiol Derivative against Carbon Steel Corrosion in HCl Solution.

The inhibiting properties of 5-(4-pyridyl)-1,3,4-oxadiazole-2-thiol (PyODT) on the corrosion of carbon steel in 1.0 M HCl solution were investigated by potentiodynamic polarization, electrochemical impedance spectroscopy, Raman spectroscopy, and SEM-EDX analysis. An approach based on machine learning algorithms and Raman data was also applied to follow the carbon steel degradation in different experimental conditions. The electrochemical measurements revealed that PyODT behaves as a mixed-type corrosion inhibitor, reaching an efficiency of about 93.1% at a concentration of 5 mM, after 1 h exposure to 1.0 M HCl solution. Due to the molecular adsorption and structural organization of PyODT molecules on the C-steel surface, higher inhibitive effectiveness of about 97% was obtained at 24 h immersion. The surface analysis showed a significantly reduced degradation state of the carbon steel surface in the presence of PyODT due to the inhibitor adsorption revealed by Raman spectroscopy and the presence of N and S atoms in the EDX spectra. The combination of Raman spectroscopy and machine learning algorithms was proved to be a facile and reliable tool for an incipient identification of the corrosion sites on a metallic surface exposed to corrosive environments.

Dissolution of Metals in Different Bromide-Based Systems: Electrochemical Measurements and Spectroscopic Investigations.

The dissolution of the main metals (Cu, Zn, Sn, Pb and Fe) found in waste printed circuit boards (WPCBs) was investigated by electrochemical corrosion measurements (potentiodynamic polarization and electrochemical impedance spectroscopy (EIS)) in different bromide-based systems that could be used as lixiviants in hydrometallurgical route of metals recovery. The analysis of the corrosion products was carried out by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements. All measurements showed that the addition of bromine in the electrolyte favors to great extents the dissolution process of all studied metals as compared to bromine-free electrolytes. In the investigated experimental conditions, the highest dissolution rates of the metals were obtained in acidic KBr solution containing 0.01 mol/L bromine and they decreased in the following order: Zn >> Sn > Pb > Fe > Cu. The XRD and XPS chemical assessment allowed the identification of the dissolution products formed on the metallic surfaces after exposure to the electrolytes. They consisted mainly of oxides in the case of Cu, Zn, Sn and Fe, while the presence of PbBr2 was also noticed on the lead surface. Based on the results of EIS and surface investigations, several models explaining the corrosion behavior of the metals were proposed and discussed. The obtained results demonstrate that all studied metals could be successfully leached using brominated solutions, providing a viable alternative for the selective and efficient recovery of the base metals from WPCBs through a multi-step hydrometallurgical processing route.